﻿using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.IO;
using System.Net;

namespace WEB
{
    public class ThumbnailImg
    {
        #region 2012-2-19 新增生成图片缩略图方法
        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="fileName">源图路径（绝对路径）</param>
        /// <param name="newFileName">缩略图路径（绝对路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>    
        public static void MakeThumbnailImage(Image img, string newFileName, int width, int height, string mode)
        {
            Image originalImage = img;
            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            if (ow < width && oh < height)
            {
                originalImage.Save(newFileName, ImageFormat.Jpeg);
                originalImage.Dispose();
                return;
            }

            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形）                
                    break;
                case "W"://指定宽，高按比例                    
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case "H"://指定高，宽按比例
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "Cut"://指定高宽裁减（不变形）                
                    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height * towidth / toheight;
                        y = 0;
                        x = (originalImage.Width - ow) / 2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width * height / towidth;
                        x = 0;
                        y = (originalImage.Height - oh) / 2;
                    }
                    break;
                default:

                    if (ow > oh)
                    {

                        toheight = (oh * width) / ow;
                        y = (height - toheight) / 2;
                    }
                    else
                    {
                        towidth = (ow * height) / oh;
                        x = (width - towidth) / 2;
                    }
                    if (y < 0 || x < 0)
                    {
                        if (width > height)
                        {
                            towidth = (ow * height) / oh;
                            x = (width - towidth) / 2;
                            y = 0;
                            toheight = height;

                        }
                        else
                        {
                            toheight = (oh * width) / ow;
                            y = (height - toheight) / 2;
                            x = 0;
                            towidth = width;
                        }

                    }
                    break;
            }

            //新建一个bmp图片
            Bitmap b = new Bitmap(towidth, toheight);
            try
            {
                //新建一个画板
                Graphics g = Graphics.FromImage(b);
                //设置高质量插值法
                g.InterpolationMode = InterpolationMode.HighQualityBicubic;
                //设置高质量,低速度呈现平滑程度
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.PixelOffsetMode = PixelOffsetMode.HighQuality;
                //清空画布并以透明背景色填充
                g.Clear(Color.Transparent);
                //在指定位置并且按指定大小绘制原图片的指定部分
                g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), new Rectangle(0, 0, ow, oh), GraphicsUnit.Pixel);

                b.Save(newFileName, System.Drawing.Imaging.ImageFormat.Jpeg);

                //SaveImage(b, , GetCodecInfo(GetFormat(newFileName).ToString().ToLower()));
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                b.Dispose();
            }
        }
        #endregion
    }
}
